353 



The volatile elements derived from the air are of such 

 little importance in this investigation, that I have not thought 

 it necessary to separate them, as they are well known to be 

 contained in the air in sufficient quantity to meet all present 

 demands ; the fixed ingredients, however, have been minutely 

 ascertained by a new process, which insures some degree of 

 accuracy. Instead of burning the substance, as is usually 

 done, I had recourse to nitric acid as an oxidizing agent, and 

 by this means discovered much more sulphur and phosphorous 

 than this plant is usually stated to contain ; this sulphur and 

 phosphorous exists in combination with the nutritive com- 

 pounds of plants, and its quantity can never be ascertained 

 by burning. It will be seen that one ton of dry clover con- 

 tains 3 lbs. 9 oz. of phosphorous, which is equal to 8 lbs. of 

 phosphoric acid, or about 16 lbs. of phosphate of lime, and, 

 as each acre will generally produce about two tons, 32 lbs. of 

 phosphate of lime would be extracted from the soil by each 

 acre of clover. Now it will be seen from the analysis of the 

 soils, both where the clover failed and where it came to 

 perfection, that a much larger quantity of phosphates are 

 contained in them than this crop requires, — hence, if these 

 phosphates can be rendered soluble, the failure of the red 

 clover crop cannot be owing to an imperfect supply of them. 

 Now it is a well-known fact that phosphate of lime is readily 

 dissolved by water containing carbonic acid gas, providing it 

 is minutely divided ; now the phosphates existing here are in 

 this state, and, consequently, can readily be dissolved by the 

 rain water, and absorbed by the roots of plants ; moreover 

 the soil where the clover failed contains quite as much phos- 

 phate as that where it came to perfection, and, as both were 

 placed under similar circumstances, we may safely conclude 

 that the phosphates have nothing to do with the failure of 

 the red clover crop. 



The next element, sulphur, has always been, since the time 



c c 2 



